The present invention relates to a contactless guided positioning table utilized in various types of precision machining apparatus, precision measurement apparatus and biotechnological apparatus.
The positioning table is used, for example, in a precision working apparatus for producing a circuit pattern of semiconductor device. In such case, the positioning table carries a semiconductor substrate and a mask in an exposure instrument which uses ultraviolet radiation for optically transferring a micro-fine image of the mask having a desired pattern onto the semiconductor substrate covered by a photosensitive material. The table is provided with a guide and a driver. For example, sliding guide face and ball screw motor drive can be used for coarse displacement, and elastic support piezoelectric element, contactless air bearing face, or linear motor can be used for fine displacement.
A precision apparatus, such as semiconductor circuit pattern exposure apparatus, requires positioning accuracy and parallel alignment accuracy on the order of 0.01 .mu.m. In order to prevent contamination by dusts and to avoid physical and chemical degradation of a substrate and photosensitive material, the table must be operated within a high vacuum. However, in the prior art, when the sliding guide face and ball screw motor drive are used for guiding and driving of the positioning table, dusts or chips may be generated due to direct contact among metal material such as steel and nonmetal material such as plastics. Further, deposition and removal of solids may be caused since lubricating oil cannot be used in vacuum.
When using the conventional contactless air bearing face, serious damage or destruction of instruments and products could not be avoided due to power supply failure, break down, leak or accident. Further, the conventional positioning table requires various addtional means for securing a desired positioning accuracy and parallel alignement accuracy.